Familial Isolated Hypoparathyroidism
Gene: GCM2 – glial cells missing 2
Protein: chorion-specific transcription factor GCMb
Clinical Characteristics
- Hypocalcemia
- Acute hypocalcemia symptoms:
- Seizures or muscle spasms
- Tingling of lips, tongue, fingers and toes
- Acute hypocalcemia symptoms:
- Chronic hypocalcemia symptoms:
- May be asymptomatic
- Muscle spasms or muscle stiffness
- Calcium and iron deposits found on CT scan of the brain
- Abnormal involuntary movements or decrease of voluntary movements
- Cataracts
- Coarse brittle hair or hair loss
- Abnormalities of the teeth
- Mental retardation
- Personality disorders
- Hyperphosphatemia
- Hypoparathyroidism
- Absence of syndromic features
Inheritance pattern:
- Autosomal recessive
- Autosomal dominant (reported in two families)
What Can Be Learned From This Test
Testing is performed by sequencing the entire coding region of the GCM2 gene. This will detect point mutations, small deletions and small insertions. It will not detect a partial or whole gene deletion or duplication.
A negative test result does not rule out a diagnosis of familial isolated hypoparathyroidism (FIH). Other genes are known to be associated with FIH and this test will only detect mutations in GCM2.
Sample Requirements
Draw 2ml–4ml of blood in EDTA/purple-top tube (minimum of 1ml–2ml for infants).
Turnaround time: 10-14 business days
CPT Codes and Cost
Full Gene Sequencing
- Code: 81479
- Cost: $500
Known Variant Testing
- Code: 81479
- Cost: $225
Additional Information